Digital Video Recorders (DVR) typically allow television viewers to schedule the recording of television programs in advance of their broadcast times. Electronic Program Guide (EPG) data containing several day's worth of program scheduling information are typically provided to the viewer's DVR. Given this information, the viewer may, via an interface provided for this purpose, configure the DVR with instructions to record a desired program that is to be broadcast on a specific channel at a given start time and for a given duration. When the start time of the program broadcast arrives, the DTV decoder automatically tunes to the indicated channel and begins recording the program with its integrated recording device or an external one for the indicated duration.
EPG data are typically broadcast at set intervals by the head-end or on an as-needed basis as the EPG data change. In accordance with the Digital Video Broadcasting (DVB) system standard, EPG data are delivered in the form of DVB service information (DVB-SI) standard Event Information Tables (EIT). In other DVB-compatible systems, private EPG data formats are used to deliver EPG data using MPEG and DVB-compatible private data channels. Various methods may be used to notify DVRs of updated EPG data, including:
Delivering updated EPG data subsequent to each change in a program schedule
Periodically delivering updated EPG data
Delivering present and following program information for each channel at the time of a program broadcast.
For the latest updated information about present and following programs, DVRs typically use DVB-SI standard EIT present/following (EIT p/f) tables or equivalent private formats.
Once a DVR is configured to record a program, a schedule change made just prior to or during the program's scheduled broadcast may result in the wrong program being recorded. For example, if a program to be recorded is cancelled or moved to another channel, the DVR will record the wrong program. If the duration of the program is extended beyond its originally scheduled duration, the end of the program will not be recorded. Similarly, if the duration of the program is extended beyond its originally scheduled duration, and the extended portion of the program is broadcast on another channel, the end of the program will not be recorded. An example that illustrates this is a tennis match of the Paris Open Championship that starts on public channel F2 at 6 p.m. and is scheduled to run until 8 p.m. Should the match run long, and a national news program is scheduled to start on channel F2 at 8 p.m., the match broadcast may switch to another public channel F3 at 8 p.m., leaving those who programmed their DVR to record the match according to the original schedule without a recording of the match finale. Another example of a schedule change made just prior to a program's being broadcast and that results in the wrong program being recorded is when a program is unexpectedly stopped and later resumed on the same channel, such as where a live sporting program is interrupted for a breaking news report and then continues with a delayed broadcast in a later time slot. Although current EIT p/f tables can be used to indicate changes in the duration of the current program, they may not be used to convey information related to a new time and broadcast location for a displaced program.